Embodiments of the present invention generally relate to rotary machines and more specifically to root inserts used in wind turbines.
Wind power is considered one of the cleanest and most environment friendly energy source presently available and hence wind turbines have gained increased attention. A modern wind turbine typically includes a tower, a nacelle, and a rotor. The rotor includes a rotatable hub and a plurality of blades. The blades are coupled to the hub by a blade root. Furthermore, the nacelle may include one or more of a shaft, a generator, and a gearbox. The shaft couples the rotatable hub to the gearbox, or directly to the generator.
The rotor blades capture kinetic energy from wind and convert the kinetic energy of the wind into rotational energy. The rotation of the blades rotates the hub of the rotor. The rotation of the hub rotates the shaft coupling the hub to the gearbox or the generator. Hence, the rotation of the shaft converts mechanical energy to electrical energy. The electrical energy may then be supplied to a utility grid.
The size of the rotor blades is a significant factor contributing to the overall capacity of the wind turbine. Specifically, an increase in the length or span of a rotor blade may generally lead to an overall increase in the energy production of a wind turbine. Accordingly, an increase in the size of the rotor blades is a motivation for adoption of wind turbines as an alternative and commercially competitive energy source. However, the increase in the size of the rotor blades may impose increased loads on various wind turbine components. For example, larger rotor blades may experience increased stresses at a connection (blade joint) between roots of the rotor blades and the hub resulting in fatigue of the blade joints.
Various methods and systems have been devised and implemented to reduce loads/stresses at connection between roots of the rotor blades and the hub. For example, some conventional systems include blades, where each blade includes a root having a flange bolted to the hub. In such systems load on the bolt is not optimally distributed. In other conventional systems, a threaded insert is bonded or infused within a blade root laminate and a bolt (i.e. the load bearing component) is screwed therein. In some other conventional systems, low-cost, low-density foam is inserted between bolt and the blade root laminate. There is a need for an enhanced root insert.